The present application claims priority to Japanese Application No. P10-251602 filed Sep. 4, 1998 and Japanese Application No. P10-334735 filed Nov. 25, 1998, which applications are incorporated herein by reference to the extent permitted by law.
The present invention relates to a semiconductor device including a semiconductor element disposed on a mounting board and a package having the mounting board, and fabrication methods thereof.
At present, semiconductor light emitting devices are being used in various industrial fields. Such a semiconductor light emitting device is generally configured such that a semiconductor light emitting element is contained in a package. The package is adapted to achieve simple handling and protection of the light emitting element, and to efficiently radiate heat generated in the light emitting element upon operation of the light emitting device. In recent years, there have been strong demands to develop a high output semiconductor light emitting device, and to develop a semiconductor light emitting device for emission of green light using a compound semiconductor composed of a compound containing a group II element and a group V1 element or a semiconductor light emitting device for emission of blue color using a compound semiconductor composed of a nitride containing nitrogen and a group III element. To meet such demands, a power supplied to the light emitting element tends to be increased, with a result that the amount of heat generation from the light emitting element becomes far larger. From this viewpoint, it is expected to enhance the heat radiation effect by means of the package for radiating the heat generation from the light emitting element.
FIG. 1 shows a related art semiconductor light emitting device having a configuration in which a semiconductor light emitting element 2220 is disposed via a sub-mount 2219 made from an insulator on a conductive mounting board 2213 made from a metal (see Japanese Patent Laid-open No. Hei8-321655). Such a semiconductor light emitting device is advantageous in that electrical connection to the semiconductor light emitting element can be easily performed by providing suitable wires on the sub-mount 2219. Specifically, the technique disclosed in this document is particularly effective for a semiconductor light emitting device in which a semiconductor light emitting element using a compound semiconductor composed of a nitride containing a group III element is formed on an insulating substrate and a p-side electrode and an n-side electrode are both provided on the side, opposed to the insulating substrate, of the light emitting element. since the sub-mount 2219 is connected to the semiconductor light emitting element 2110, the p-side electrode and the n-side electrode may be connected to pins by way of the sub-mount 2219, to thereby make the area required for wire bonding large on the sub-mount 2219. A current can be injected into the semiconductor light emitting device from the p-side electrode and the n-side electrode connected to the two pins shown in FIG. 1 via the sub-mount 2219.
FIG. 2 shows another related art method for electrical connection of a semiconductor light emitting device including a semiconductor light emitting element using a compound semiconductor composed of a nitride containing a group III element. Referring to FIG. 2, a p-side electrode of the semiconductor light emitting device is connected to a left pin and an n-side electrode thereof is connected to a third pin (not shown) via a sub-mount 2129 and a conductive mounting board 2121. With this electrical connection, a current can be injected into the semiconductor light emitting device. Further, a photodetector (not shown) for monitoring optical output of the semiconductor light emitting device is disposed on the conductive mounting board 2121, wherein a first electrode of the photodetector is connected, together with the semiconductor light emitting device, to the common third pin not shown, and a second electrode of the photodetector is connected to a right pin. With this configuration, the optical output of the semiconductor light emitting device can be monitored by the photodetector.
The above-described technique, however, has a problem. Since an insulator is lower in both thermal conductivity and electrical conductivity than a metal, the p-side electrode and the n-side electrode provided on the same side are prevented from being short-circuited by using the insulating sub-mount 2219 or 2129, however, the heat radiation characteristic of the device is reduced. As a result, the temperature of the semiconductor light emitting element is raised, thereby degrading the stable operation and reliability of the device for a long-period of time.
A known semiconductor device of this type is configured such that a wiring portion is formed on a flat surface of a conductive board via a thin insulating film, and a p-side electrode of a semiconductor light emitting element is connected to the conductive board and an n-side electrode of the element is connected to the wiring portion. Such a semiconductor device, however, is disadvantageous in that since the wiring portion is formed on the conductive board via the thin insulating film, it is impossible to ensure the sufficient insulation of the wiring portion from the conductive board.
An object of the present invention is to provide a semiconductor device and a package, which are capable of ensuring a high heat radiation effect while preventing short-circuit between electrodes, and fabrication methods thereof.
To achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor device including a conductive mounting board having a recessed portion and a projecting portion disposed on said conductive mounting board; an insulating mounting board disposed on said recessed portion of said conductive mounting board; and a semiconductor element having one portion disposed on said conductive mounting board and the other portion disposed on said insulating mounting board. With this configuration, it is possible to ensure electrical insulation of the semiconductor element and radiate heat generated in the semiconductor element via the conductive mounting board, and hence to suppress temperature rise of the semiconductor element and thereby ensure a stable operational state of the device for a long-period of time. As a result, it is possible to improve the reliability of the semiconductor device.
In this semiconductor device, preferably, the first electrode is disposed on a portion, on the side where the active layer is provided, of the first conduction type semiconductor layer and the second electrode is disposed on a portion, on the side opposed to the active layer, of the second conduction type semiconductor layer; and also the first electrode is disposed on the insulating mounting board and the second electrode is disposed on the conductive mounting board. With this configuration, it is possible to shorten the distance between the active layer and the conductive mounting board and hence to positively radiate heat generated in the active layer via the conductive mounting board. As a result, it is possible to suppress temperature rise of the semiconductor element and to prevent short-circuit between the first electrode and the second electrode of the semiconductor element.
In the semiconductor device, preferably, the semiconductor element is configured such that a plurality of the light emitting portions are formed on the same substrate. With this configuration, it is possible to radiate heat generated in each active layer via the conductive mounting board, and hence to suppress thermal interference between the light emitting portions. As a result, it is possible to suppress an increase in threshold current and a reduction in luminous efficiency in each light emitting portion, and hence to ensure a high quality of the device for a long-period of time.
In the semiconductor device, a separating portion is preferably provided on the conductive mounting board at a position between the recessed portion and the projecting portion. With this configuration, it is possible to more effectively ensure the insulation of the semiconductor element.
In the semiconductor device, a position fixing portion is preferably provided on the conductive mounting board in such a manner as to provide the recessed portion between the projecting portion and the position fixing portion. with this configuration, it is possible to easily and accurately dispose the insulating mounting board on the conductive mounting board.
In the semiconductor device, the insulating mounting board may be formed on the recessed portion of the conductive mounting board by deposition. With this configuration, it is possible to easily and accurately dispose the insulating mounting board at a low cost.
According to a second aspect of the present invention, there is provided a package including a conductive mounting board having on its one surface a recessed portion and a projecting portion; and an insulating mounting board disposed on the recessed portion of the conductive mounting board. With this configuration, it is possible to ensure electrical insulation of the semiconductor element by the presence of the insulating mounting board and to ensure the heat radiation characteristic by the presence of the conductive mounting board.
In this package, preferably, the conductive mounting board has the recessed portion on which the insulating mounting board is to be disposed and the projecting portion on which the semiconductor element is to be disposed. With this configuration, it is possible to ensure electrical insulation of the semiconductor element by the insulating mounting board disposed on the recessed portion and to positively radiate heat generated in the semiconductor element via the conductive mounting board.
According to a third aspect of the present invention, there is provided a method of fabricating a semiconductor device, including the steps of: forming a conductive mounting board having on its one surface a recessed portion and a projecting portion; forming an insulating mounting board disposed on the recessed portion of the conductive mounting board; forming a semiconductor element; and disposing one portion of the semiconductor element on the conductive mounting board and also disposing the other portion of the semiconductor element on the insulating mounting board. With this configuration, it is possible to easily fabricate the semiconductor device, and hence to easily realize the semiconductor device of the present invention.
According to a fourth aspect of the present invention, there is provided a method of fabricating a package including the steps of: forming a conductive mounting board having on its one surface a recessed portion and a projecting portion; and forming an insulating mounting board disposed on the recessed portion of the conductive mounting board. With this configuration, it is possible to easily fabricate the package, and hence to easily realize the package of the present invention.
The method of fabricating the package, preferably, includes the step of: forming a conductive mounting board having on its one surface a recessed portion on which an insulating mounting board is to be disposed and a projecting portion on which a semiconductor element is to be disposed. With this configuration, it is possible to easily fabricate the package, and hence to easily realize the package of the present invention.
According to a fifth aspect of the present invention, there is provided a semiconductor device including: a semiconductor element having a plurality of stacked semiconductor layers and also having a first electrode and a second electrode provided on the same side in the stacking direction; and a conductive mounting board for supporting the semiconductor element in a state in which one of the first electrode and the second electrode of the semiconductor element is fixed to the conductive mounting board. With this configuration, it is possible to prevent short-circuit between the first electrode and the second electrode and to positively radiate heat generated in the semiconductor element via the conductive mounting board. This makes it possible to suppress temperature rise of the semiconductor element and to keep a stable operational state of the device for a long-period of time. As a result, it is possible to improve the reliability of the semiconductor device.
In this semiconductor device, preferably, the first electrode is provided on a portion, on the second conduction type semiconductor layer side, of the first conduction type semiconductor layer; and the second electrode is provided on a portion, on the side opposed to the first conduction type, of the second conduction type semiconductor layer and is also fixed to the conductive mounting board. With this configuration, it is possible to shorten the distance between the active layer and the conductive mounting board, and hence to more effectively radiate heat generated in the semiconductor element via the conductive mounting board.
In the semiconductor device, preferably, a side surface of the conductive mounting board is tilted, from the mounting surface side to the opposed side, toward one of the first electrode and the second electrode. With this configuration, it is possible to broaden a space near the other electrode, and hence to facilitate the electrical connection of the other electrode to a power source.
In the semiconductor device, preferably, the conductive mounting board is located to be shifted rightwardly from the center of the supporting surface when the mounting surface of the conductive mounting board is directed upwardly. With this configuration, it is possible to easily fix one of the first electrode and the second electrode to the conductive mounting board, and to easily connect the other electrode to a power source in accordance with Japanese Industrial Standards.
In the semiconductor device, preferably, the support has the fixing groove for fixing the conductive mounting board with the mounting surface directed downwardly. With this configuration, it is possible to facilitate the electrical connection of the other of the first electrode and the second electrode to a power source.
According to a sixth aspect of the present invention, there is provided a package including: a conductive mounting board having a mounting surface on which a semiconductor element is to be disposed; and a support, having a supporting surface perpendicular to the mounting surface, for supporting the conductive mounting board by the supporting surface; wherein the conductive mounting board is located in such a manner as to be shifted rightwardly or leftwardly from the center of the supporting surface when the mounting surface is directed upwardly; and the conductive mounting board has a side surface at an end, near the center of the support, in the direction parallel to the mounting surface and the supporting surface, the side surface being tilted, from the mounting surface side to the opposed side, toward the opposed end of the mounting surface. With this configuration, in the case of mounting the semiconductor element having the first electrode and the second electrode on the same side, one of the first electrode and the second electrode can be easily fixed to the conductive mounting board. This makes it possible to prevent short-circuit of the semiconductor element and to positively radiate heat generated in the semiconductor element via the conductive mounting board. Further, it is possible to broaden a space near the other electrode, and hence to facilitate the electrical connection of the other electrode to a power source.
According to a seventh aspect of the present invention, there is provided a method of fabricating a semiconductor device, including the steps of: stacking a plurality of semiconductor layers and providing a first electrode and a second electrode on the same side in the stacking direction, to form a semiconductor element; and disposing the semiconductor element on the conductor mounting board while fixing one of the first electrode and the second electrode on the conductive mounting board. with this configuration, it is possible to easily fabricate the semiconductor device of the present invention, and hence to easily realize the semiconductor device of the present invention.
In the above fabrication method, preferably, the semiconductor element is located on the lower side and the conductive mounting board is located on the upper side and in such a state the other electrode is connected to a pin by means of the wire. With this configuration, it is possible to facilitate electrical connection of the wire, and hence facilitate the electrical connection of the other electrode to a power source.